Air-conditioning device, railway vehicle air-conditioning device, and method for controlling air-conditioning device

ABSTRACT

An air-conditioning device includes (i) a compressor, (ii) an outdoor heat exchanger, (iii) an indoor heat exchanger and an electronic expansion valve, (iv) a bypass passage connecting a middle compression chamber and a low pressure space, the middle compression chamber accommodating a refrigerant undergoing compression by the compressor, the low pressure space accommodating the refrigerant having a pressure lower than a pressure of the refrigerant in the middle compression chamber, (v) a bypass valve to open or close the bypass passage, and (vi) a controller to set a degree of opening of the electronic expansion valve based on a degree of superheat of a refrigerant. Based on a change from a closed state of the bypass valve to an open state, the controller corrects the degree of opening of the electronic expansion valve to a value that is less than a value set by the degree-of-superheat control.

TECHNICAL FIELD

The present disclosure relates to an air-conditioning device, a railway vehicle air-conditioner device, and a method for controlling the air-conditioning device.

BACKGROUND ART

In an air-conditioning device, a degree of opening of an expansion valve is adjusted based on a degree of superheat calculated from pressure and temperature of a refrigerant to keep a circulation amount of the refrigerant a proper value in order to enable efficient exchange heat by an indoor heat exchanger. Electronic expansion valves by which the circulation amount of the refrigerant can be precisely controlled are widely used (for example, refer to Patent Literature 1).

CITATION LIST Patent Literature

Patent Literature 1: Unexamined Japanese Patent Application Kokai Publication No. H10-38350 (refer to paragraph 0023 and FIG. 2)

SUMMARY OF INVENTION Technical Problem

Incidentally, capacity control mechanisms for controlling a compressor capacity are widely applied to air-conditioning devices in order to adjust cooling and heating performance. Examples of the capacity control mechanisms include an inverter-type capacity control mechanism that is able to perform stepless control of the capacity of the compressor and a mechanical capacity control mechanism that is able to perform mainly two-stage control of the capacity of the compressor.

In an air-conditioning device provided with such a capacity control mechanism, a change of a capacity of a compressor causes transient fluctuation in compressor suction pressure or refrigerant pressure. For example, a reduction in the capacity of the compressor causes a decrease in an amount of refrigerant discharged from the compressor. As a result, the suction pressor of the compressor increases, thereby causing a temporary increase in a circulation amount of the refrigerant in the indoor heat exchanger. There is a risk that the increase in the circulation amount of the refrigerant in the indoor heat exchanger may cause liquid flood back, in which a portion of the refrigerant that the indoor heat exchanger fails to evaporate returns to the compressor.

As described above, although the circulation amount of the refrigerant is usually adjusted based on the degree of superheat, for improvement of detection accuracy, a relatively large time constant is set for each of various sensors used for calculation of the degree of superheat. As a result, the influence of the change of the capacity of the compressor as a fluctuation in degree of superheat is delayed. Accordingly, in the method described in Patent Literature 1, even if the suction pressure of the compressor or the refrigerant pressure transiently fluctuates due to the change of the capacity of the compressor, there is a risk that the liquid flood back may occur before the fluctuation in the pressure is detected as the fluctuation in the degree of superheat and the degree of opening of the expansion valve changes.

Particularly, such fluctuation is more notably for a compressor equipped with the mechanical capacity control mechanism than with in the inverter-type capacity control mechanism that is able to finely control a rotational frequency.

In order to solve the aforementioned problem, an objective of the present disclosure is to achieve: an air-conditioning device that is able to further suppress occurrence of liquid flood back due to a change of a capacity of the compressor than conventional devices; and an air-conditioning device for railway vehicles.

Solution to Problem

An air-conditioning device according to the present disclosure includes a compressor, an outdoor heat exchanger, an indoor heat exchanger and an electronic expansion valve that are connected to one another via refrigerant piping to constitute a refrigeration cycle, wherein: the air-conditioning device includes (i) a bypass passage communicatively connecting a middle compression chamber and a low pressure space, the middle compression chamber being a chamber to accommodate a refrigerant undergoing compression by the compressor, the low pressure space being a space to accommodate the refrigerant having a pressure lower than a pressure of the refrigerant in the middle compression chamber, (ii) a bypass valve to open or close the bypass passage, and (iii) a controller to execute degree-of-superheat control in which a degree of opening of the electronic expansion valve is set based on a degree of superheat of a refrigerant; and, based on a change from a closed state of the bypass valve to an open state of the bypass valve, the controller starts restriction processing in which the degree of opening of the electronic expansion valve is corrected to a value that is less than the value set by the degree-of-superheat control.

The air-conditioning device according to the present disclosure includes a refrigeration circuit in which a compressor, an outdoor heat exchanger, an indoor heat exchanger and an electronic expansion valve are connected to one another via the refrigerant piping, wherein: the air-conditioning device includes a middle compression chamber to accommodate a refrigerant undergoing compression by the compressor, a bypass passage communicating with a low pressure space to accommodate a refrigerant having a pressure lower than a pressure of the refrigerant in middle compression chamber, a bypass valve to open or close the bypass passage, and a controller to execute degree-of-superheat control in which a degree of opening of the electronic expansion valve is set based on a degree of superheat of the refrigerant; and, upon detecting a change request to change a state of the bypass valve from an open state to a closed state, the controller starts facilitation processing in which the degree of opening of the electronic expansion valve is corrected to a value that is greater than the value set by the degree-of-superheat control, and, afterward, the controller changes the open state of the bypass valve to the closed state of the bypass valve.

Advantageous Effects of Invention

According to the present disclosure, based on the change from the closed state of the bypass valve to the open state of the bypass valve, the degree of opening of the electronic expansion valve is corrected to a value that is less than the value set by the degree-of-superheat control, thereby enabling a decrease in the circulation amount of the refrigerant before a change in the capacity of the compressor has an influence on the fluctuation in the degree of superheat. As a result, in comparison to a conventional device, the device of the present disclosure can suppress occurrence of the liquid flood back due to the change of the capacity of the compressor.

An increase in the capacity of the compressor results in an increase in an amount of refrigerant discharged from the compressor, whereby the amount of the refrigerant in the compressor temporarily decreases. Due to the decrease of the amount of the refrigerant in the compressor, a sliding member of the compressor slides with the sliding member in direct contact with another component, whereby there is a possibility of occurrence of an abnormality such as galling. In regard to this point, according to the present disclosure, the facilitation processing is started before the open state of the bypass valve is changed to the closed state of the bypass valve, where the facilitation processing is processing in which the degree of opening of the electronic expansion valve is corrected to a value that is greater than the value set by the degree-of-superheat control, and thus the amount of the refrigerant existing in the compressor can be increased. This enables suppression of a sharp decrease of the amount of refrigerant in the compressor due to the change from the open state of the bypass valve to the closed state of the bypass valve. Accordingly, the occurrence of an abnormality such as galling caused by the sliding movement of sliding member that is in direct contact with the other component can be suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating an air-conditioning device according to Embodiment 1 of the present disclosure;

FIG. 2 is a cross-sectional view illustrating a compressor and a capacity control mechanism according to Embodiment 1 of the present disclosure;

FIG. 3 is a flow chart illustrating control of the air-conditioning device according to Embodiment 1 of the present disclosure;

FIG. 4 illustrates timing charts of a change in a degree of opening of an electronic expansion valve, changes in a set temperature and in a detected temperature, a pressure of refrigerant, and a an operation mode by restriction processing and facilitation processing for the air-conditioning device according to Embodiment 1 of the present disclosure;

FIG. 5 is a flow chart illustrating control of the air-conditioning device according to Embodiment 2 of the present disclosure;

FIG. 6 illustrates timing charts of a change in a degree of opening of an electronic expansion valve, changes in a set temperature and in a detected temperature, a change in a pressure of refrigerant, and a change in an operation mode by restriction processing and facilitation processing for the air-conditioning device according to Embodiment 2 of the present disclosure;

FIG. 7 is a flow chart illustrating control of the air-conditioning device according to Embodiment 3 of the present disclosure;

FIG. 8 is a schematic view illustrating a railway vehicle according to Embodiment 4 of the present disclosure;

FIG. 9 is a side view illustrating a compressor according to Embodiment 4 of the present disclosure; and

FIG. 10 is a schematic view illustrating an air-conditioning device according to another embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure are described with reference to attached drawings. Components that are the same or equivalent are assigned the same reference signs throughout the drawings. Duplicate descriptions are appropriately abbreviated or omitted. Also, for illustrative purposes, each of the drawings may illustrate a component such that the proportion of the size or the shape of the component to the size or shape of another component is exaggerated.

Embodiment 1

An air-conditioning device 10 according to Embodiment 1 of the present disclosure is described with reference to FIGS. 1 to 4. As illustrated in FIG. 1, the air-conditioning device 10 according to the present embodiment includes: a compressor 1 to compress a refrigerant; an electronic expansion valve 2 to reduce pressure of the refrigerant; an outdoor heat exchanger 3 to function as a condenser during a cooling operation and to exchange heat between outdoor air and the refrigerant; an indoor heat exchanger 4 to function as an evaporator during the cooling operation and to exchange heat between indoor air and the refrigerant; and a controller 7 to control these components. The controller 7 is connected to a room temperature sensor 14 to measure a temperature in a room equipped with the air-conditioning device 10 and to a remote controller 15 by which a user performs on-off control of the air-conditioning device 10 and inputs a desired set temperature To.

The compressor 1 compresses the refrigerant sucked into the compressor, and discharges the refrigerant in the high temperature and high pressure state. The compressor 1 of the present embodiment is configured as a scroll compressor that includes a mechanical capacity control mechanism 60, and is operated at a predetermined constant frequency of compression per unit of time (seconds). The mechanical capacity control mechanism 60 is described later in detail.

The outdoor heat exchanger 3 is an outdoor-air heat exchanger to exchange heat between outdoor air taken from outside the room and the refrigerant, and makes heat move from the refrigerant to ambient air during the cooling operation. The indoor heat exchanger 4 is an indoor-air heat exchanger to exchange heat between indoor air and the refrigerant, and makes heat move from indoor air to the refrigerant during the cooling operation.

The electronic expansion valve 2 is a component to reduce the pressure of the refrigerant to expand the refrigerant so that the refrigerant has a low temperature and a low pressure, and is an expansion valve for which the degree of opening is variably controllable. Preferably, a linear expansion valve (LEV) is used as the electronic expansion valve 2.

The compressor 1, the outdoor heat exchanger 3, the electronic expansion valve 2, and the indoor heat exchanger 4 are connected to one another via a refrigerant piping 20 in which the refrigerant flows, thus forming a refrigerant circuit in which the refrigerant circulates. During the cooling operation, the refrigerant circulates in the refrigerant piping 20 in a direction indicated by a solid arrow in FIG. 1. The refrigerant is compressed by the compressor 1, so that the refrigerant turns into a gas having a high temperature and a high pressure. After the refrigerant is condensed and liquefied by the outdoor heat exchanger 3, the pressure of the refrigerant is decreased by expanding the refrigerant by the electronic expansion valve 2, so that the refrigerant is in a two-phase state of the refrigerant having a low temperature and low pressure. Afterward, the refrigerant is evaporated and gasified by the indoor heat exchanger 4, and then returns to the compressor 1. When the indoor air passes through the indoor heat exchanger 4, the indoor air exchanges heat with the low-temperature refrigerant, thereby decreasing temperature of the indoor air, and then the indoor air is supplied to the interior of the room.

A pipe of the refrigerant piping 20 that connects the compressor 1, the outdoor heat exchanger 3, and the electronic expansion valve 2 to one another is referred to as a high pressure refrigerant pipe 26 through which the high pressure refrigerant discharged from the compressor 1 passes. Also, a pipe of the refrigerant piping 20 that connects the electronic expansion valve 2, the indoor heat exchanger 4 and the compressor 1 to one another is referred to as a low pressure refrigerant pipe 25 through which the refrigerant having a pressure lower than the pressure in the higher pressure refrigerant pipe 26 passes.

The high pressure refrigerant pipe 26 is connected to a high pressure control refrigerant line 21 into which a portion of the high-pressure refrigerant discharged from the compressor 1 flows. On the other hand, the low pressure refrigerant pipe 25 is connected to a low pressure control refrigerant line 22 into which a portion of the low-pressure refrigerant sucked by the compressor 1 flows. The high pressure control refrigerant line 21 and the low pressure control refrigerant line 22 are connected to a control pressure introduction pipe 23 that communicates with the capacity control mechanism 60.

A high pressure control valve 8 is disposed in the high pressure control refrigerant line 21, and a low pressure control valve 9 is disposed in the low pressure control refrigerant line 22. Each of the high pressure control valve 8 and the low pressure control valve 9 includes a solenoid valve that can open or close to switch between circulation and non-circulation of the refrigerant.

Both the high pressure control valve 8 and the low pressure control valve 9 are connected to the controller 7 and are opened or closed based on a command from the controller 7. The controller 7 opens one of the high pressure control valve 8 and the low pressure control valve 9 is opened and closes the other. In a case in which the high pressure control valve 8 is closed and the low pressure control valve 9 is opened, a portion of the low-temperature refrigerant flowing in the low temperature refrigerant pipe 25 flows into the control pressure introduction pipe 23. In a case in which the high pressure control valve 8 is opened and the low pressure control valve 9 is closed, a portion of the high-temperature refrigerant flowing in the high temperature refrigerant pipe 26 flows into the control pressure introduction pipe 23.

Next, the compressor 1 of the present embodiment and a structure of the capacity control mechanism 60 included in the compressor 1 are described in detail with reference to FIGS. 1 and 2.

As illustrated in FIG. 2, the compressor 1 includes a sealed container 50 forming an outer frame of the compressor 1. Also, the compressor 1 includes a fixed scroll 51 that is provided with, as components disposed in the sealed container 50 and functioning as sliding members for compressing the refrigerant, a fixed spiral-shaped body 54 and an orbiting scroll 52 that is provided with an orbiting spiral-shaped body 55. The fixed spiral-shaped body 54 and the orbiting spiral-shaped body 55 are joined such that the fixed spiral-shaped body 54 and the orbiting spiral-shaped body 55 intermesh with each other, thereby forming compression chambers P. A compression chamber P that is located at the central portion communicates with the high pressure refrigerant pipe 26.

The orbiting scroll 52 eccentrically orbits relative to the fixed scroll 51 at a previously predetermined constant speed, and the compression chambers P are gradually reduced in size from outside low-pressure compression chambers toward inside high-pressure compression chambers. As illustrated by the solid arrows in FIG. 2, the refrigerant that flows through the low pressure refrigerant pipe 25 into the compressor 1 flows from the outside low-pressure compression chambers of the compression chambers P into the compression chambers P and then flows toward the inside high-pressure compression chambers while being compressed by the orbital movement of the orbiting scroll 52. Afterward, the refrigerant is discharged through a discharge path 53 to the high pressure refrigerant path 26.

The fixed scroll 51 is provided with the capacity control mechanism 60 that is to control the capacity of the compressor 1. The capacity control mechanism 60 is configured to include (i) a back pressure passage 61 into which either of the low-pressure refrigerant or the high-pressure refrigerant flows from the control pressure introduction pipe 23, (ii) a back pressure chamber 62 housing the bypass valve 64 and communicating with the back pressure passage 61, (iii) a coil spring 63 elastically supporting the bypass valve 64, and (iv) a bypass passage 65 that is formed in the fixed scroll 51 and used for returning, to a low-pressure space, the refrigerant present in the middle compression chamber and undergoing the compression process. The middle compression chamber is freely determined based on a location at which the bypass passage 65 is formed. The low-pressure space is any portion of the inner space of the compressor 1 in which refrigerant exists that has a pressure lower than the pressure of the refrigerant in the middle compression chamber. The low-pressure space may be located outside the compression chambers P or may be a low-pressure compression chamber located nearer to the outside than the middle compression chamber is. In the present embodiment, the bypass valve 64 is elastically supported by the coil spring 63. However, the coil spring 63 may be replaced with another elastic body such as a rubber component.

Refrigerant pressure in the control pressure introduction pipe 23 and refrigerant pressure in the middle compression chamber act on the above-described bypass valve 64. When the low-pressure refrigerant flows into the back pressure passage 61, the refrigerant pressure in the control pressure introduction passage 23 becomes lower than the refrigerant pressure in the middle compression chamber, and the bypass valve 64 opens. In this case, a portion of the refrigerant in the middle compression chamber returns through the bypass passage 65 to the low-pressure space. An operation mode in which, by opening the bypass valve 64, a portion of the refrigerant in the middle compression chamber returns to the low-pressure space in this manner is referred to as an unloading (UL) mode.

When the high-pressure refrigerant flows into the back pressure passage 61, the refrigerant pressure in the control pressure introduction valve 23 becomes higher than the refrigerant pressure in the middle compression chamber, and the bypass valve 64 closes. In this case, after the whole of the refrigerant in the middle compression chamber is transferred to the high-pressure compression chambers and then is compressed, the compressed refrigerant is discharged to the discharge path 53. An operation mode in which, by closing the bypass valve 64, the whole of the refrigerant in the middle compression chamber is discharged to the discharge path 53 in this manner is referred to as a full-loading (FL) mode.

Referring back to FIG. 1, the description of the present embodiment is continued. The low-pressure refrigerant pipe 25 is provided with (i) a refrigerant temperature sensor 11 to detect a refrigerant temperature Tm of the refrigerant sucked by the compressor 1 and (ii) a refrigerant pressure sensor 12 to detect a refrigerant pressure Pm of the refrigerant, where the sensor 12 correspond to a pressure detector recited in claims. The refrigerant temperature sensor 11, the refrigerant pressure sensor 12, the high pressure control valve 8, the low pressure control valve 9, the electronic expansion valve 2, the room temperature sensor 14 and the remote controller 15 are connected to the controller 7.

The controller 7 includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM) and the like that are not illustrated in the drawings, and stores various types of programs, a function, fixed data and the like that are used for driving the air-conditioning device 10. The controller 7 executes the various types of programs using the above-described function and data, data inputted from various types of sensors, and the like, so that the controller 7 drives the high-pressure control valve 8 and the low-pressure control valve 9 to make the high-pressure control valve 8 and the low-pressure control valve 9 open or close, adjusts a degree of opening of the electronic expansion valve 2, and executes processing for other operations for driving the air-conditioning device 10.

For example, the controller 7 calculates a degree SH1 of superheat of the refrigerant flowing into the compressor 1 from (i) the refrigerant temperature Tm detected by the refrigerant temperature sensor 11 and (ii) the refrigerant pressure Pm detected by the refrigerant pressure sensor 12, and then the controller 7 adjusts the degree of opening of the electronic expansion valve 2 based on the calculated degree SH1 of superheat.

The controller 7 compares the calculated degree SH1 of superheat with a previously-stored threshold SHT and adjusts the degree of opening of the electronic expansion valve 2 based on a difference between the degree SH1 of superheat and the threshold SHT. In a case in which the degree SH1 of superheat is greater than the threshold SHT, the degree of opening of the electronic expansion valve 2 increases with increased difference between the degree SH1 of superheat and the threshold SHT, so that the degree SH1 of superheat is reduced. In a case in which the degree SH1 of superheat is less than the threshold STH, the greater the difference between the degree SH1 of superheat and the threshold STH is, the more the degree of opening of the electronic expansion valve 2 is reduced, so that the degree SH1 of superheat is increased. In a case in which SH1 is equal to the threshold STH, the degree of opening of the electronic expansion valve 2 remains unchanged. The threshold SHT is generally set to 5 to 10° C., without particular limitation.

Also, the controller 7 uses the below-described formula (1) to calculate a difference ΔT between (i) a temperature Tr detected by the room temperature sensor 14 and (ii) a set temperature To set by a user through the remote controller 15, and then determines an operation mode of the compressor 1 based on this difference ΔT.

ΔT=Tr−To   (1)

The controller 7 stores the upper limit value Tu of and the lower limit value T1 of the difference ΔT. In a case in which the controller 7 determines that the difference ΔT is equal to or greater than the upper limit value Tu, the controller 7 makes the compressor 1 to drive in the full-loading mode. On the other hand, in a case in which the controller 7 determines that the difference ΔT is less than the lower limit value Tl, the controller 7 makes the compressor 1 to drive in the unloading mode. In contrast, in a case in which the difference ΔT is not less than the lower limit value T1 and is less than the upper limit value Tu, the controller makes the air-conditioning device 10 to drive in the current operation mode without changing the operation mode.

Incidentally, when a closed state of the bypass valve 64 is changed to an open state of the bypass valve 64 in order to change the operation mode from the full-loading mode to the unloading mode, an amount of the refrigerant discharged from the compressor 1 decreases rapidly, so that an amount of the refrigerant flowing in the low-temperature refrigerant pipe 25 temporarily rapidly increases. Since a relatively large time constant is set for the refrigerant temperature sensor 11 and the refrigerant pressure sensor 12 for the purpose of accurately detecting the degree SH1 of superheat, the influence by a change of the amount of the flow of the refrigerant accompanied by the change of the operation mode occurs as fluctuation in the degree SH1 of superheat is delayed. Occurrence of such a time lag causes the amount of the refrigerant flowing in the low-pressure refrigerant pipe 25 to increase beyond the heat-exchange capacity of the indoor heat exchanger 4 before the change of the amount of the flow of the refrigerant is detected as the fluctuation in the degree SH1 of superheat, thereby causing a risk that so-called liquid flood back may occur, where the liquid flood back is a phenomenon in which a portion of the refrigerant, without evaporating, flows into the compressor 1.

Therefore, in the present embodiment, based on a change of operation modes of the compressor 1 from the full-loading mode to the unloading mode, that is, based on a change from the closed state of the bypass valve 64 to the open state of the bypass valve 64, the controller 7 starts restriction processing in which the degree of opening of the electronic expansion valve 2 is corrected, by subtraction, to a degree of opening that is smaller, by a given degree θa of opening, than a degree of opening set based on the degree SH1 of superheat. The given degree θa of opening is a degree of opening necessary for suppressing an increase in the amount of the flow of the refrigerant caused by the change from the closed state of the bypass valve 64 to the open state of the bypass valve 64, and the given degree θa of opening is freely selected. Without particular limitation, degree of opening of the electronic expansion valve 2 is preferably corrected, by subtraction of the given degree θa of opening, to a value of a degree of opening at which the electronic expansion valve 2 permits flow of the refrigerant by the amount that corresponds to the lower limit of the heat-exchange capacity of the indoor heat exchanger 4. If the given degree θa of opening is too great, a pressure of the refrigerant in the compressor 1 rapidly decreases, and thus the orbiting spiral-shaped body 55 slides directly on the fixed spiral-shaped body 54 without the refrigerant existing therebetween, thereby causing a risk that an abnormality such as galling may occur. Therefore, the given degree θa of opening is preferably set in consideration of the amount of the refrigerant in the compressor 1.

In contrast, when the open state of the bypass valve 64 is changed to the closed state of the bypass valve 64 so that the operation mode is changed from the unloading mode to the full-loading mode, the amount of the refrigerant discharged from the compressor 1 temporarily increases even if the amount of the refrigerant sucked by the compressor 1 remains unchanged, so that the amount of the refrigerant in the compressor 1 is temporarily rapidly reduced. The rapid reduction in the amount of the refrigerant in the compressor 1 causes the orbiting spiral-shaped body 55 to slide directly on the fixed spiral-shaped body 54 without the refrigerant existing therebetween, thereby causing a risk that an abnormality such as galling may occur.

Therefore, in a case in which a request to change from the unloading mode to the full-loading mode is detected, that is, upon detection, during the unloading mode, that the difference ΔT becomes equal to or greater than the upper limit value Tu, the controller 7 changes the operation mode of the compressor 1 to the full-loading mode after executing facilitation processing in which the degree of opening of the electronic expansion valve 2 is corrected by adding a given degree of opening θb to the degree of opening set based on the degree SH1 of superheat. The given degree of opening θb is a degree of opening necessary for suppressing a rapid decrease in the amount of the refrigerant in the compressor 1 that is caused by the change from the open state of the bypass valve 64 to the closed state of the bypass valve 64, and the given degree of opening θb is freely set. For example, after the correction by addition of the given degree θb of opening, the degree of opening of the electronic expansion valve 2 is preferably set to a value at which the electronic expansion valve 2 permits flow of the refrigerant in the amount corresponding to the upper limit of the heat-exchange capacity of the indoor heat exchanger 4, without particular limitation.

Next, operation of the air-conditioning device 10 according to the present embodiment is described with reference to a flowchart illustrated in FIG. 3. In parallel with the operation based on the flowchart of FIG. 3, the controller 7 is taken to calculate the degree SH1 of superheat based on the refrigerant temperature Tm detected by the refrigerant temperature sensor 11 and the refrigerant pressure Pm detected by the refrigerant pressure sensor 12 and then to constantly calculate an appropriate degree of opening of the electronic expansion valve 2 based on this degree SH1 of superheat.

First, upon a user operating the remote controller 15 to execute control for turning on the air-conditioning device 10, driving of the compressor 1 starts. Operation of the air-conditioning device 10 is started by driving the compressor 1.

Upon starting of the driving of the compressor 1, the controller 7 first calculates, based on the above-described formula (1), the difference (ΔT) between the temperature Tr detected by the room temperature sensor 14 and the set temperature inputted by the user (Step S10).

Next, the controller 7 determines whether the calculated difference ΔT is equal to or greater than the previously-stored upper limit value Tu (Step S11). In a case in which the controller 7 determines that the difference ΔT is less than the upper limit value Tu (No in Step S11), the controller 7 determines whether the difference ΔT is less than the lower limit value Tl (Step S12).

In a case in which the controller 7 determines that the difference ΔT is not less than the lower limit value Tl (No in Step S12), that is, in a case in which the controller 7 determines that the difference ΔT is less than the upper limit value Tu and is equal to or greater than the lower limit value Tl, a change of the operation mode of the compressor 1 is not made. In this case, the controller 7 does not make a correction of the degree of opening of the electronic expansion valve 2.

On the other hand, upon determination that the difference ΔT is less than the lower limit value Tl (Yes in Step S12), the controller 7 changes the operation mode of the compressor 1 to the unloading mode. The controller 7 first determines whether the operation mode of the compressor 1 is the full-loading mode (Step S13).

In the present embodiment, in a case in which the low pressure control valve 9 is opened and the high pressure control valve 8 is closed, the bypass valve 64 is in an open state, so that the controller determines that the compressor 1 is in the unloading mode. However, in a case in which the low pressure control valve 9 is closed and the high pressure control valve 8 is opened, the bypass valve 64 is in a closed state, so that the controller determines that the compressor 1 is in the full-loading mode. In the present embodiment, although the determination as to whether the compressor 1 is in the unloading mode or in the full-loading mode is made by determining whether either of the low pressure control valve 9 and the high pressure control valve 8 is in the open state, the determination of the operation mode of the compressor 1 may be made by another publically well-known manner. For example, the determination of the operation mode of the compressor 1 may be made on the basis of the refrigerant pressure Pm in the control pressure introduction pipe 23 or using a sensor to detect opening or closing of the bypass valve 64, without particular limitation, and other publicly-well know manners may be used.

In a case in which the controller 7 determines that the operation mode of the compressor 1 is not the full-loading mode (No in Step S13), that is, in a case in which the controller 7 determines that the operation mode of the compressor 1 is the unloading mode, the operation mode is unchanged, and correction of the degree of opening of the electronic expansion valve 2 is not made.

However, in a case in which the controller 7 determines that the operation mode of the compressor 1 is the full-loading mode (Yes in Step S13), the controller 7 changes the operation mode of the compressor 1 to the unloading mode (Step S14) and then starts restriction processing (Step S15). Upon starting the control processing, the controller 7 corrects the degree of opening of the electronic expansion valve by subtracting the given degree of opening θa from the degree of opening of the electronic expansion valve 2 that is calculated based on the degree SH1 of superheat, and then the degree of opening of the electronic expansion valve 2 is set to the corrected degree of opening.

Next, the controller 7 determines whether an elapsed time period Ta of time elapsed since the start of the restriction processing is equal to or longer than a given time period T1 (Step S16). The given time period T1 is a time period that is sufficient to reduce the refrigerant pressure Pm, and is freely set. For example, without particular limitation, the given time period T1 is preferably a period of time taken by a certain amount of refrigerant to pass through the electronic expansion valve 2, where the certain amount of refrigerant corresponds to an amount of refrigerant that is returned from the middle compression chamber to the low-pressure space.

Upon determination that the elapsed time period Ta is shorter than the given time period T1 (No in Step S16), the restriction processing continues, and upon determination that the elapsed time period Ta is equal to or longer than the given time period T1 (Yes in Step S16), the restriction processing ends (Step S17). That is, the correction of the degree of opening of the electronic expansion valve 2 ends.

In contrast, in a case in which the controller 7 determines that the difference ΔT is equal to or greater than the upper limit value Tu (Yes in Step S11), the controller 7 determines, in the above-described manner, whether the compressor 1 is in the unloading mode (Step S18).

Upon determination that the compressor 1 is in the unloading mode (Yes in Step S18), on the grounds that the difference ΔT is equal to or greater than the upper limit value Tu and the operation mode is the unloading mode, the controller 7 determines that a request to change the operation mode from the unloading mode to the full-loading mode is made.

At this time in time, the controller 7 starts facilitation processing before changing the operation mode to the full-loading mode (Step S19). Upon starting the facilitation processing, the controller 7 corrects the degree of opening of the electronic expansion valve by adding the given degree of opening θb to the degree of the opening of the electronic expansion valve 2 calculated based on the degree SH1 of superheat, and then the controller 7 sets the degree of opening of the electronic expansion valve 2 to a degree of opening obtained by the correction.

Next, the controller 7 determines whether an elapsed time period Tb of time elapsed since the start of the facilitation processing is equal to or longer than a given time period T2 (Step S20). The given time period T2 is a period of time that it takes for the compressor 1 to secure therein an amount of refrigerant that does not cause malfunction of the compressor 1 despite a rapid increase in an amount of refrigerant discharged from the compressor 1 due to a change of the operation mode, and is freely set. For example, without particular limitation, the given time period T2 is preferably a period of time that is takes for the compressor 1 to secure therein an amount of the refrigerant corresponding to the amount of refrigerant that is returned from the middle compression chamber to the low-pressure space.

Upon determination that the elapsed time period Tb is shorter than the given time period T2 (No in Step S20), the facilitation processing continues. However, upon determination that the elapsed time period Tb is equal to or longer than the given time period T2 (Yes in Step S20), the facilitation processing (Step S21). That is, the controller 7 terminates the correction of the degree of opening of the electronic expansion valve 2. Also, the operation mode of the compressor 1 is changed to the full-loading mode (Step S21).

On the other hand, in a case in which the controller 7 determines that the compressor 1 is not in the unloading mode (No in Step S18), that is, in a case in which the controller 7 determines that the compressor 1 is in the full-loading mode, the operation mode of the compressor 1 is not changed. In this case, the controller 7 does not correct the degree of opening of the electronic expansion valve 2.

Next, the controller 7 determines whether the operation of the air-conditioning device 10 is finished (Step S22). In a case in which the controller 7 determines that the operation of the air-conditioning device 10 is finished (Yes in Step S22), the controller 7 terminates this process. In a case in which the controller 7 determines that the air-conditioning device 10 is still in operation (No in Step S22), processing returns to Step S10 and this processing continues.

FIG. 4 illustrates one example of each of transitions of (a) the degree of opening of the electronic expansion valve 2, (b) the temperature Tr detected by the room temperature sensor 14 and the set temperature To, (c) the refrigerant pressure Pm detected by the refrigerant pressure sensor 12, and (d) the operation mode of the compressor 1, in a case in which the process illustrated in FIG. 3 is performed.

In (a) of FIG. 4, one example of the transition of the degree of opening of the electronic expansion valve 2 caused by execution of the above-described restriction processing and the above-described facilitation processing is plotted as a solid line, and one example of the transition of the degree of opening of the electronic expansion valve 2 without execution of the above-described restriction processing and facilitation processing is plotted as a dashed double-dotted line. In (b) of FIG. 4, one example of the transition of the set temperature To set by the user using the remote controller 15 is plotted as a solid line, and one example of the transition of the temperature Tr detected by the room temperature sensor 14 is plotted as a dash-dotted line. In (c) of FIG. 4, one example of the transition of the refrigerant pressure Pm caused by execution of the above-described restriction processing and facilitation processing is plotted as a solid line, and one example of the transition of the refrigerant pressure Pm without execution of the above-described restriction processing and facilitation processing is plotted as a long dashed double-dotted line. In (d) of FIG. 4, one example of the transition of the operation mode of the compressor 1 caused by execution of the above-described restriction processing and the above-described facilitation processing is plotted as a solid line, and one example of the transition of the operation mode of the compressor 1 without execution of the above-described restriction processing and facilitation processing is plotted as a dash-dotted line.

As illustrated in FIG. 4, when the difference ΔT between the set temperature To and the detected temperature Tr is equal to or greater than the upper limit value Tu, the compressor 1 is operated in the full-loading mode (times t0 to t1).

When the difference ΔT further becomes less than the lower limit value Tl after becoming less than the upper limit value Tu, the controller 7 changes the operation mode of the compressor 1 from the full-loading mode to the unloading mode. At this point in time, the controller 7 starts the restriction processing in which the given angle θa is subtracted from the degree of opening of the electronic expansion valve 2 calculated based on the degree SH1 of superheat (time t1). This restriction processing continues over the given time period T1 (time t1 to t2).

Upon executing the restriction processing, the degree of opening of the electronic expansion valve 2 decreases, thereby causing a reduction in an amount of the refrigerant flowing in the low pressure refrigerant pipe 25. As a result, a temporary rise in the refrigerant pressure Pm is suppressed. After the given time period T1 elapses, the controller 7 terminates the restriction processing (time t2).

Afterward, when the set temperature To is changed and thus the difference ΔT becomes equal to or greater than the upper limit value Tu (time t3), the controller 7 determines that a request to change the operation mode is made. In this case, before the operation mode is changed from the unloading mode to the full-loading mode, the controller 7 starts the facilitation processing in which the degree of opening of the electronic expansion valve 2 is corrected by adding the given degree θb of opening to the degree of opening calculated from the degree SH1 of superheat (the time t3). The facilitation processing continues over the given time period T2 (time t3 to t4). The operation mode is maintained as the unloading mode.

Upon executing the facilitation processing, the degree of opening of the electronic expansion valve 2 is increased, thereby causing an increase in an amount of the refrigerant flowing in the low pressure refrigerant pipe 25, and thus the refrigerant pressure Pm increases (time t3 to t4). After the given time period T2 elapses, the controller 7 terminates the facilitation processing (time t4). That is, the controller 7 terminates the correction of the degree of opening of the electronic expansion valve 2. Also, the controller 7 changes the operation mode of the compressor 1 from the unloading mode to the full-loading mode.

Embodiment 1 as described above can exhibit the following effects.

Since the restriction processing in which the given degree θa of opening is subtracted from the degree of opening of the electronic expansion valve 2 is started based on the change from the closed state of the bypass valve 64 to the open state of the bypass valve 64, an amount of flow of the refrigerant can be reduced before the change in the capacity of the compressor 1 is reflected in the fluctuation of the degree SH1 of superheat. As a result, occurrence of liquid flood back due to a change of the capacity of the compressor 1 can be suppressed more than conventional devices.

Since the facilitation processing in which the given degree θb of opening is added to the degree of opening of the electronic expansion valve 2 is started before the open state of the bypass valve 64 is changed to the closed state of the bypass valve 64, an amount of the refrigerant existing in the compressor 1 can be increased before the change in the capacity of the compressor 1. As a result, it is possible to suppress occurrence of a situation in which, due to the rapid reduction in the amount of the refrigerant existing in the compressor 1, the orbiting spiral-shaped body 55 slides on the fixed spiral-shaped body 54 with the fixed spiral-shaped body 54 and the orbiting scroll 50 directly coming into contact with each other.

Since the restriction processing is executed over the given time period T1, occurrence of hunting is suppressed, and thus occurrence of liquid flood back can be more favorably suppressed.

Since the facilitation processing is executed over the given time period T2, the occurrence of hunting is suppressed, and thus the present embodiment can more preferably suppress occurrence of the situation in which the orbiting spiral-shaped body 55 slides on the fixed spiral-shaped body 54 with the fixed spiral-shaped body 54 and the orbiting scroll 50 directly coming into contact with each other.

Embodiment 2

A method of controlling an air-conditioning device 10 according to Embodiment 2 is described with reference to FIGS. 5 and 6 together with FIGS. 1 to 4. Unless otherwise stated, reference signs that are the same as in Embodiment 1 denote components that are the same, and steps that are the same are assigned step reference numbers that are the same. Accordingly, detailed description of these components and these steps is omitted as appropriate.

FIG. 5 illustrates a control flowchart of control of the air-conditioning device 10 according to Embodiment 2. Operation of a controller 7 according to Embodiment 2 is described with reference to FIG. 5. In the control flowchart illustrated in FIG. 5, Steps S15 to S17 of the flowchart of FIG. 3 are replaced with Steps S30 to S34, and the other steps are the same. Accordingly, description of the contents of similar control is omitted.

After changing the operation mode of the compressor 1 to the unloading mode (Step S14), the controller 7 determines whether the refrigerant pressure Pm detected by the refrigerant pressure sensor 12 is equal to or greater than a threshold P1 (corresponding to a first given pressure recited in claims) (Step S30). It is preferable that the threshold P1 corresponds to a refrigerant pressure at which the refrigerant the amount of which corresponds to the upper limit of the heat-exchange capacity of the indoor heat exchanger 4 passes.

In a case in which the controller 7 determines that the refrigerant pressure Pm is less than the threshold P1 (No in Step S30), the controller 7 determines whether an elapsed time period Tc since a change of the operation mode to the unloading mode is equal to or longer than a given time period T3 (Step S31). The given time period T3 is a period of time for a temporarily-increasing suction pressure to return to a steady state after a change of the operation mode of the compressor 1 to the unloading mode, and is freely set. The given time period T3, without particular limitation, is preferably set to a time period during which a certain amount of refrigerant passes through the electronic expansion valve 2, where the certain amount of refrigerant corresponds to an amount of refrigerant that is returned from the middle compression chamber to the low-pressure space.

In a case in which the controller 7 determines that the elapsed time period Tc of time elapsed since the change of the operation mode to the unloading mode is shorter than the given time period T3 (No in Step S31), processing returns to Step S30. However, in a case in which the controller 7 determines that the elapsed time period Tc since the change of the operation mode to the unloading mode is equal to or longer than the given time period T3 (Yes in Step S31), the processing is terminated for now.

In contrast, in a case in which the controller 7 determines that the refrigerant pressure Pm is equal to or greater than the threshold P1 (Yes in Step S30), the controller 7 starts the restriction processing (Step S32). Subsequently, the controller 7 determines whether an elapsed time period Ta since the start of the restriction processing is equal to or longer than the given time period T1 (Step S33). In a case in which the controller 7 determines that the elapsed time period Ta since the start of the restriction processing is less than the given time period T1 (No in Step S33), processing returns to Step S33. In a case in which the controller 7 determines that the elapsed time period Ta since the start of the restriction processing is equal to or longer than the given time period T1 (Yes in Step S33), this processing (Step S34) ends.

FIG. 6 illustrates one example of each of transitions of (a) the degree of opening of the electronic expansion valve 2, (b) the temperature Tr detected by the room temperature sensor 14 and the set temperature To, (c) the refrigerant pressure Pm detected by the refrigerant pressure sensor 12, and (d) the operation mode of the compressor 1, in a case in which the process illustrated in FIG. 5 is performed.

In (a) of FIG. 6, one example of the transition of the degree of opening of the electronic expansion valve 2 caused by execution of the above-described restriction processing and the above-described facilitation processing is plotted as a solid line, and one example of the transition of the degree of opening of the electronic expansion valve 2 without execution of the above-described restriction processing and the above-described facilitation processing is plotted as a dashed double-dotted line. In (b) of FIG. 6, one example of the transition of the set temperature To set by the user using the remote controller 15 is plotted as a solid line, and one example of the transition of the temperature Tr detected by the room temperature sensor 14 is plotted as a dash-dotted line. In (c) of FIG. 6, one example of the transition of the refrigerant pressure Pm caused by execution of the above-described restriction processing and facilitation processing is plotted as a solid line, and one example of the transition of the refrigerant pressure Pm without execution of the above-described restriction processing and facilitation processing is plotted as a dashed double-dotted line. In (d) of FIG. 6, one example of the transition of the operation mode of the compressor 1 caused by execution of the above-described restriction processing and facilitation processing is plotted as a solid line, and one example of the transition of the operation mode of the compressor 1 without execution of the above-described restriction processing and facilitation processing is plotted as a dash-dotted line.

As illustrated in FIG. 6, when the operation mode is changed from the full-loading mode to the unloading mode (time t1) after operating the compressor 1 in the full-loading mode (a time t0 to the time t1), the controller 7 monitors the refrigerant pressure Pm over the given time period T3 (time t1 to t7). When the refrigerant pressure Pm is equal to or greater than the threshold P1, the controller 7 starts the restriction processing in which a correction is made by subtracting the given degree θa of opening from the degree of opening of the electronic expansion valve 2 calculated based on the degree SH1 of superheat (time t5). This restriction processing continues over the given time period T1 (time t5 to t6).

The present embodiment can exhibit the following effect in addition to the effects described in Embodiment 1.

In a case in which the controller determines that the refrigerant pressure Pm is equal to or greater than the threshold P1, the restriction processing is started, and, in a case in which the refrigerant pressure Pm is less than the threshold P1, the restriction processing is not started. Accordingly, the restriction processing is started even if the refrigerant pressure Pm is sufficiently low, thereby suppressing an excessive reduction in an amount of the circulating refrigerant. Accordingly, a reduction in the cooling capacity can be suppressed.

Embodiment 3

A method of controlling an air-conditioning device 10 according to Embodiment 3 is described with reference to FIG. 7 together with FIGS. 1 to 3. Unless otherwise stated, reference signs that are the same as in Embodiment 1 denote components that are the same, and steps that are the similar are assigned step reference numbers that are the same, and accordingly detailed description of such is omitted as appropriate.

FIG. 7 is an explanatory drawing illustrating a control flowchart of control of the air-conditioning device 10 according to Embodiment 3. Operation of a controller 7 according to Embodiment 3 is described with reference to FIG. 7. In the control flowchart illustrated in FIG. 7, processing for starting up the air-conditioning device 10 (steps S1 to S3) is added to the flowchart of FIG. 3, and the other steps of the flowchart of FIG. 7 are the same as those in FIG. 3. Accordingly, description of the contents of control that are similar is omitted.

At the time when the air-conditioning device 10 is started up, the refrigerant in the compressor 1 has a low temperature, so that the refrigerant in the compressor 1 is in a state in which the refrigerant easily dissolves into lubricant. When a large amount of the refrigerant dissolves in the lubricant in the compressor 1, there is a risk of occurrence of so-called oil foaming that is a phenomenon in which the refrigerant dissolving in the lubricant rapidly evaporates due to a reduction in a pressure in the compressor 1 when the compressor 1 is started up. Occurrence of the oil foaming may result in risk that the frothy lubricant in the compressor 1 is discharged to the outside of the compressor 1.

Accordingly, in the present embodiment, the degree of opening of the electronic expansion valve 2 is fixed at a given degree θc of opening (corresponding to a start-up degree of opening recited in claims) at the time when the air-conditioning device 10 is started up, thereby increasing an amount of the refrigerant flowing into the compressor 1 during the start-up of the air-conditioning device 10, and suppressing a reduction in pressure in the compressor 1. Also, the operation mode of the compressor 1 is set to the unloading mode during the start-up of the air-conditioning device 10, whereby an amount of the refrigerant discharged from the compressor 1 is reduced, and thus a reduction in the pressure in the compressor 1 is more favorably suppressed.

The processing at the start of operation of the air-conditioning device 10 according to the present embodiment is described with reference to FIG. 7. Upon starting the operation of the compressor 1 and then starting the operation of the air-conditioning device 10, the controller 7 fixes the degree of opening of the electronic expansion valve 2 at the previously-predetermined given degree θc of opening (Step 51). The given degree θc of opening is a degree of opening necessary for supplying to the interior of the compressor 1 an amount of the refrigerant that does not cause occurrence of the oil foaming despite a reduction in pressure in the compressor 1 caused by discharging the refrigerant from the compressor 1 during the start-up of the compressor 1. The given degree θc of freely set. The given degree θc of opening is most preferably a maximum degree of opening that the electronic expansion valve 2 can have.

Next, the controller 7 sets the operation mode of the compressor 1 to the unloading mode (Step S2). Afterward, the controller 7 determines whether an elapsed time period Td since the start of the operation of the air-conditioning device 10 is equal to or longer than a given time period T4 (Step S3). The given time period T4 is a period of time necessary for causing the air-conditioning device to make a transition to a steady state after finishing the start-up of the air-conditioning device 10. For example, the given time period T4 may be set to a previously determined period of time for the degree SH1 of superheat to converge at a certain range after the start-up of the air-conditioning device 10, where such a period of time may be previously found by measurement. Also, the given time period T4 may be set to a previously determined period of time for the refrigerant discharged from the compressor 1 to circulate in the refrigerant piping 20 to return to the compressor 1 again, where such a period of time may be previously found by measurement.

In a case in which the controller 7 determines that the elapsed time period Td of time elapsed since the start of the operation of the air-conditioning device 10 is shorter than the given time period T4 (No in Step S3), processing returns to return to Step S3. However, in a case in which the controller 7 determines that the elapsed time period Td since the start of the operation of the air-conditioning device 10 is equal to or longer than the given time period T4 (Yes in Step S3), processing proceeds to Step S10.

The present embodiment can exhibit the following effect in addition to the effects described in Embodiments 1 and 2.

Since the degree of opening of the electronic expansion valve 2 is fixed at the given degree θc of opening and the operation mode of the compressor 1 is set to the unloading mode at the time when the air-conditioning device 10 is started up, a reduction in the pressure in the compressor 1 during the start-up of the air-conditioning device 10 can be suppressed. Accordingly, occurrence of liquid flood back and oil foaming during the start-up of the air-conditioning device 10 can be suppressed.

Embodiment 4

An air-conditioning device 10 according to Embodiment 4 is described with reference to FIGS. 8 and 9. In Embodiment 4, an example of an application of the air-conditioning device 10 of Embodiment 1 or 2 to a railroad vehicle is described. Unless otherwise stated, reference signs that are the same as in Embodiment 1 or 2 denote components that are the same, and steps that are the similar are assigned step reference numbers. Accordingly, detailed description of such components and steps is omitted as appropriate.

FIG. 8 is a view illustrating the appearance of a vehicle 70 equipped with the air-conditioning device 10 of the present embodiment. FIG. 8 illustrates a case in which the air-conditioning device 10 is mounted on a roof of the vehicle. However, the air-conditioning device 10 may be disposed under a floor of the vehicle.

As illustrated in FIG. 9, in the present embodiment, the compressor 1 is arranged such that the discharge side of the compressor is located upward so that a center shaft line of the compressor 1 inclines at an inclination angle A relative to a horizontal plane. The inclination angle A is preferably 0° to 15°, more preferably 0° to 10°, and most preferably 0° to 5°.

In a case in which the air-conditioning device 10 is mounted on the railroad vehicle, space for disposal of the air-conditioning device 10 is limited, and particularly, space for disposing the air-conditioning device 10 in the vertical direction is often insufficient. Accordingly, height of the air-conditioning device 10 is to be reduced.

Lubricant 31 for lubricating the fixed spiral-shaped body 54, the orbiting spiral-shaped body 55 and the like is stored in the compressor 1. If the compressor 1 is arranged such that the shaft center line of the compressor 1 is parallel to the horizontal plane for the purpose of the reduction in height of the air-conditioning device, there is a risk that the lubricant 31 together with the compressed refrigerant may discharge into the refrigerant piping 20. Also, in a case in which the liquid flood back occurs, there is a risk that the lubricant 31 may discharge into the refrigerant piping 20.

In regard to this point, since the compressor 1 is arranged such that the shaft center line of the compressor 1 inclines at the inclination angle A relative to the horizontal plane in the present embodiment, discharge of the lubricant can be suppressed further in comparison to arrangement of the shaft center line parallel to the horizontal plane. Also, as described in Embodiments 1 to 3, the occurrence of the liquid flood back can be suppressed by control of the electronic expansion valve 2, so that the discharge of the lubricant can be favorably suppressed.

The present embodiment exhibits the following effects in addition to exhibiting effects similar to the effects described in Embodiments 1 to 3.

According to the present embodiment, the reduction in height of the air-conditioning device 10 can be achieved and the discharge of the lubricant 31 can be suppressed.

Another Embodiment

As illustrated in FIG. 10, an air-conditioning device 10 according to the present embodiment may include an accumulator 28 disposed in the middle of the refrigerant piping 20 connecting the indoor heat exchanger 4 and the compressor 1, a four-way valve 29 to switch flow passages of the refrigerant, a hot gas bypass 27 to bypass the refrigerant discharged from the compressor 1 to the inflow side of the compressor 1, and a solenoid 32 to switch between passage and non-passage of the refrigerant through the hot gas bypass 27.

In the present embodiment, during a heating operation, through a switching operation of the four-way valve 29, the refrigerant is compressed by the compressor 1 to become a gas at high temperature and pressure, and then the refrigerant is condensed to be liquefied by the indoor heat exchanger 4. Afterward, the refrigerant is made to expand by using the electronic expansion valve 2 to reduce the pressure of the refrigerant, so that the refrigerant becomes two phases at low temperature and pressure. Afterward, the refrigerant is evaporated and gasified by the outdoor heat exchanger 3, passes through the accumulator 28, and then returns to the compressor 1. When air in the vehicle passes through the indoor heat exchanger, the air in the vehicle exchanges heat with the high temperature refrigerant, so that the air in the vehicle becomes high temperature air for return to the interior of the vehicle. The cooling operation is different from the heating operation only in a direction of flow of the refrigerant in the refrigerant circuit, as described above. Other matters and the structures of the operations are the same.

According to the present embodiment, the lubricant flows in the hot gas bypass path 27 and then flows into the compressor 1 again even if the lubricant discharges from the compressor 1, so that the depletion of the lubricant in the compressor 1 can be suppressed. Also, since the liquid refrigerant is stored in the accumulator, occurrence of the liquid flood back can be effectively suppressed.

In each of the above-described embodiments, the value ΔT is taken to be a value obtained by subtracting the set temperature To from the detected temperature Tr. However, in the present embodiment, the difference ΔT is preferably set to the absolute value of the value obtained by subtracting the set temperature To from the detected temperature Tr.

In each of the above-described embodiments, the high pressure control valve 8 and the low pressure control valve 9 are solenoid valves to switch between passage and non-passage of the refrigerant. However, the present disclosure is not limited to such solenoid valves. For example, the high pressure valve 8 and the low pressure valve 9 may be linear valves configured as electronic valves having an adjustable degree of opening.

In the above-described embodiments, the degree SH1 of superheat is calculated based on the temperature of and the pressure of the refrigerant flowing into the compressor 1. However, the present disclosure is not limited to such configuration. Temperature sensors may be disposed at an inlet portion and an outlet portion of the indoor heat exchanger 4, and the degree SH1 of superheat may be calculated based on temperatures detected by these temperature sensors. Even in this case, the air-conditioning device according to the present embodiment can exhibit effects similar to those described in the above-described embodiments.

In Embodiment 3, the example in which the air-conditioning device is mounted on the railroad vehicle is described. However, this configuration is not limiting, and the air-conditioning device may be installed in a house, a building, a warehouse, an automobile or the like. Even in these cases, the device according to the present embodiment can exhibit effects similar to those described in Embodiment 3.

In the restriction processing of each of the above-described embodiments, the degree of opening of the electronic expansion valve 2 is corrected by subtracting the previously-determined given degree θa of opening from the degree of opening set based on the degree SH1 of superheat. However, the restriction processing of the present disclosure is not limited to such a manner. The restriction processing used in the present disclosure may be any processing in which the degree of opening of the electronic expansion valve 2 is corrected so as to be less than a degree of opening that is set on the basis of the degree SH1 of superheat. For example, the degree of opening of the electronic expansion valve 2 may be corrected to the minimum degree of opening possible for the electronic expansion valve 2. Alternatively, the higher the refrigerant pressure Pm at the start of the restriction processing, the more the given degree θa of opening may be increased. Alternatively, after the refrigerant pressure Pm is monitored during execution of the restriction processing, the given degree θa of opening may be adjusted based on a result of such monitoring.

In the restriction processing of each of the above-described embodiments, the restriction processing is terminated upon continuation of the restriction processing for the given time period T1. However, a time period of the restriction processing of the present disclosure is not limited to the given time period T1 and can be changed as appropriate. For example, the higher the refrigerant pressure Pm at the start of the restriction processing, the longer period the given time period T1 may be set to. Alternatively, the restriction processing may be terminated when the refrigerant pressure Pm reduces to a given pressure P2 of the refrigerant. The pressure P2 of the refrigerant is preferably set to the pressure that the refrigerant has in a case in which an amount of the refrigerant corresponding to the upper limit of the heat-exchange capacity of the indoor heat exchanger 4 passes through the low pressure refrigerant pipe 25.

In the facilitation processing of each of the above-described embodiments, the degree of opening of the electronic expansion valve 2 is corrected by adding the previously-determined given degree θb of opening to the degree of opening set based on the degree SH1 of superheat. However, the facilitation processing of the present disclosure is not limited to such configuration. The facilitation processing used in the present disclosure may be any processing in which the degree of opening of the electronic expansion valve 2 is corrected so as to be greater than a degree of opening that is set on the basis of the degree SH1 of superheat. For example, the degree of opening of the electronic expansion valve 2 may be corrected to the maximum degree of opening possible for the electronic expansion valve 2. Alternatively, the lower the refrigerant pressure Pm at the start of the facilitation processing, the more the given θb of opening may be reduced. Alternatively, after the refrigerant pressure Pm is monitored during execution of the facilitation processing, the given degree θb of opening may be adjusted based on a result of the monitoring of the refrigerant pressure Pm.

In the facilitation processing of each of the above-described embodiments, the facilitation processing is terminated upon continuation over the previously-defined given time period T2. However, a time period during which the facilitation processing of the present disclosure is executed is not limited to the time period T2 and can be changed as appropriate. For example, the lower the refrigerant pressure Pm at the start of the facilitation processing, the longer the given time period T2 may be set. Alternatively, the facilitation processing may be terminated when the refrigerant pressure Pm rises to a previously-determined pressure P3 of the refrigerant.

REFERENCE SIGNS LIST

-   1 Compressor -   2 Electronic expansion valve -   3 Outdoor heat exchanger -   4 Indoor heat exchanger -   7 Controller -   8 High pressure control valve -   9 Low pressure control valve -   10 Air-conditioning device -   11 Refrigerant temperature sensor -   12 Refrigerant pressure sensor -   14 Room temperature sensor -   15 Remote controller -   20 Refrigerant piping -   21 High pressure control refrigerant line -   22 Low pressure control refrigerant line -   23 Control pressure introduction pipe -   25 Low pressure refrigerant pipe -   26 High pressure refrigerant pipe -   27 Hot gas bypass path -   28 Accumulator -   29 Four-way valve -   32 Solenoid valve -   50 Sealed container -   51 Fixed scroll -   52 Orbiting scroll -   53 Discharge path -   54 Fixed spiral-shaped body -   55 Orbiting spiral-shaped body -   60 Capacity control mechanism -   61 Back pressure passage -   62 Back pressure chamber -   63 Coil spring -   64 Bypass valve -   65 Bypass passage 

1. An air-conditioning device including a refrigerant circuit in which a compressor, an outdoor heat exchanger, an indoor heat exchanger and an electronic expansion valve are connected to one another via refrigerant piping, the air-conditioning device comprising: a bypass passage communicatively connecting a middle compression chamber and a low pressure space, the middle compression chamber being a chamber to accommodate a refrigerant undergoing compression by the compressor, the low pressure space being a space to accommodate the refrigerant having a pressure lower than a pressure of the refrigerant in the middle compression chamber; a bypass valve to open or close the bypass passage; and a controller to execute degree-of-superheat control in which a degree of opening of the electronic expansion valve is set based on a degree of superheat of the refrigerant, wherein based on a change from a closed state of the bypass valve to an open state of the bypass valve, the controller starts restriction processing in which the degree of opening of the electronic expansion valve is corrected to a value that is less than the value set by the degree-of-superheat control.
 2. The air-conditioning device according to claim 1, wherein the controller comprises a pressure detector for detecting a pressure of a refrigerant that flows into the compressor, and a condition for a start of the restriction processing is that the pressure as a result of the detection by the pressure detector is equal to or higher than a first given pressure.
 3. An air-conditioning device including a refrigerant circuit in which a compressor, an outdoor heat exchanger, an indoor heat exchanger and an electronic expansion valve are connected to one another via refrigerant piping, the air-conditioning device comprising: a bypass passage communicatively connecting a middle compression chamber and a low pressure space, the middle compression chamber being a chamber to accommodate a refrigerant undergoing compression by the compressor, the low pressure space being a space to accommodate the refrigerant having a pressure lower than a pressure of the refrigerant in the middle compression chamber; a bypass valve to open or close the bypass passage; and a controller to execute degree-of-superheat control in which a degree of opening of the electronic expansion valve is set based on a degree of superheat of the refrigerant, wherein upon detecting a change request to change a state of the bypass valve from an open state to a closed state, the controller starts facilitation processing in which the degree of opening of the electronic expansion valve is corrected to a value that is greater than the value set by the degree-of-superheat control, and the controller subsequently changes the state of the bypass valve from the open state to the closed state.
 4. The air-conditioning device according to claim 1, wherein upon start-up of the compressor, the degree of opening of the electronic expansion valve is set to a start-up degree of opening, and the bypass valve is set to the open state.
 5. An air-conditioning apparatus for a railroad vehicle comprising the air-conditioning device according to claim 1, wherein the compressor is arranged such that the compressor is inclined relative to a horizontal plane.
 6. A method of controlling an air-conditioning device including (i) a refrigerant circuit in which a compressor, an outdoor heat exchanger, an indoor heat exchanger and an electronic expansion valve are connected to one another via refrigerant piping, (ii) a bypass passage communicatively connecting a middle compression chamber and a low pressure space, the middle compression chamber being a chamber to accommodate a refrigerant undergoing compression by the compressor, the low pressure space being a space to accommodate the refrigerant having a pressure lower than a pressure of the refrigerant in the middle compression chamber, and (iii) a bypass valve to open or close the bypass passage, the method comprising: a degree-of-superheat control step of setting a degree of opening of the electronic expansion valve based on a degree of superheat of the refrigerant; and a restriction step of correcting, based on a change from a closed state of the bypass valve to an open state of the bypass valve, the degree of opening of the electronic expansion valve to a value less than the value set in the degree-of-superheat control step.
 7. The method according to claim 6, further comprising: facilitation step of correcting, when a change request to change a state of the bypass valve from an open state to a closed state is detected, the degree of opening of the electronic expansion valve to a value that is greater than the value set in the degree-of-superheat control step. 